Poseidon held a performance advantage inside the Ethereum Foundation's post-quantum design. Researcher Justin Drake said that advantage is now gone. Advances in compact proofs erased it, and the Foundation is pivoting away from Poseidon in its post-quantum plan as a result.
The compact proof advance that changed the calculus
Drake attributed the shift directly to progress in compact proofs. Poseidon's prior edge over other options had made it a logical fit for the post-quantum roadmap. That edge closed as compact proof technology caught up. The performance argument for Poseidon no longer holds.
What the pivot means for $ETH protocol design
The Ethereum Foundation's post-quantum plan is now moving without Poseidon as a component. Drake, identified in the source as a researcher, is the named voice behind this assessment. No replacement primitive was specified. The Foundation's post-quantum work continues on the updated basis that compact proof performance fills the gap Poseidon was previously selected to cover.